Method for thermoforming and stacking hollow objects

ABSTRACT

A method for the thermoforming of hollow objects having a base from a sheet of thermoplastics material, which effects in one single predetermined operating cycle, the production of a pressed object by hot forming and cutting out of the object or objects between one half of a movable double female mould which is located in the forming area opposite a male die, movement of the female half of the mould, said half containing therewithin the thermoformed object or objects, towards a corresponding discharge area alternately to one side or the other of the forming area; picking up the object or objects from the female half of the mould located in corresponding discharge area and transferring each object to a plurality of receiving formers of a shape corresponding to the mould, which formers can move sequentially stepwise along a track, sequential movement of the formers to at least one workstation or handling station at the same time as the female mould moves back to place its other half opposite the male die in order to produce a subsequently formed object, and performing at least one processing or handling operation on all the objects carried by at least one former at the same time as the next formed object is produced.

This is a continuation of application Ser. No. 08/181,184 filed Jan. 13,1994 now U.S. Pat. No. 5,453,237, which is a divisional of applicationSer. No. 07/937,362, filed Aug. 28, 1992, abandoned.

This invention relates to a method and apparatus for the thermoformingof hollow cup-shaped objects such as beakers, goblets, cups, tubs andthe like, from a sheet of thermoplastics material, and their removalfrom the press in which they are produced.

BACKGROUND OF THE INVENTION

As is known, so-called "thermoforming" machines, fall into two quiteseparate classes depending upon their method of operation; firstly thereare thermoforming machines which form and cut the sheet at separateworkstations and secondly there are machines which form and cut thesheet at a single workstation. Such machines are used in the productionof objects of thermoplastics material, e.g. "disposable" objects, from asheet of hot pressed material.

This invention relates to a method and apparatus which falls into thissecond class, in that the shaping or forming of objects and theirseparation from the sheet of starting material is effected at a singleworkstation.

The state of the art for thermoforming methods and apparatusincorporating a single forming station, separation from the initialsheet and subsequent removal from the press, is represented byconventional single station machines and those according to U.S. Pat.No. 4,560,339 which will be briefly described hereinafter with referenceto FIGS. 1 to 13 of the accompanying drawings, in which:

FIG. 1 is a side view in diagrammatic form of a thermoforming machinehaving an upper male die and a single lower female mould shown in theopen press position prior to forming;

FIG. 2 is a side view of the machine of FIG. 1 shown with the pressclosed during the forming stage;

FIG. 3 is a view similar to that shown in FIG. 2 with the press closedduring the cutting stage;

FIG. 3a is a schematic view of a detail of FIG. 3 shown on an enlargedscale;

FIG. 4 is a side view of the machine of FIG. 3 shown with the press openafter the formed object has been cut out but still remains in the press;

FIG. 5 is a similar view to that in FIG. 4 but at a subsequent stage inwhich the pressed object is removed from the female mould and removedfrom the pressing area to a stacking collector;

FIG. 6 is a side view of a variation of the machine shown in FIG. 5having a multiple row of moulds which discharge in bulk to a separatestacker;

FIGS. 7 to 10 show diagrammatic views of another variation of themachine shown in FIG. 5, in which the pressed objects are removed fromthe pressing area by means of a suction plate which can be placedbetween the male and female parts of the press;

FIG. 11 diagrammatically illustrates a plate which can lift a pluralityof articles pressed in a single pressing operation by suction, used inthe machine according to FIGS. 7 to 10;

FIG. 12 diagrammatically illustrates a front view of a thermoformingmachine having a single upper male die and a double lower female mouldwhich moves alternately beneath the male die; and

FIG. 13 includes a diagram which illustrates the stages andopening/closing cycle times for a thermoforming press having a singlefemale mould.

The thermoforming cycle in machines which carry out forming and cuttingat a single workstation can be described schematically as follows.

Stage 1: Sheet feed with the press open (FIG. 1).

A portion of sheet material A is delivered from a feed role (not shown)and is heated by irradiators B, e.g. infrared sources, and caused toadvance between the open portions of the press, that is into thethermoforming area, in the direction of arrow F. The press consists ofan upper male part or die M₁ and a lower female part M₂. Both parts M₁and M₂ may be single or multiple, in which latter case several objects Ocan be obtained from each pressing operation.

Stage 2: Forming while the press is closed (FIG. 2).

The lower female part M₂ rises against fixed male die M₁ and object O ishot formed by causing rough shaping die M_(1p) to enter the cavityM_(2c) of female mould part M₂ and thereafter injecting compressed airor applying negative pressure through a hole FO in male die M₁. Thecompressed air causes the material A around rough forming die M_(1p) toadhere to the side wall of cavity M_(2c) and movable base M_(2f)thereof. Then cavity M_(2c) is cooled by a water cooling circuitgenerically indicated by C, and object O is also cooled and thensubjected to a process of progressive structural and dimensionalstabilisation.

Stage 3: Cutting (FIGS. 3 and 3a).

In this stage, all the lower part M₂ of the press moves a distance ST,usually 1.5 mm (FIG. 3a) towards upper die M₁, which is sufficient toseparate the edge BO of object O from starting sheet material A.

The three stages described above are common to all thermoformingmachines which shape and cut at a single workstation, or forming area(see diagram in FIG. 13). However a distinction is made between twoclasses of thermoforming machines on the basis of the differentarrangements used to remove thermoformed objects O from the female mouldM₂ and subsequent operations (counting, stacking, etc.). The former havea single female mould M₂, the latter has a double female mould, one onthe left M_(2c) and one on the right M_(2d), which are integral witheach other, as will be explained below with reference to FIG. 12 and theobject of Italian Patent No. 1,073,243.

The cutting stage (stage 3) completes the closed press cycle ofoperations (FIG. 13).

After this stage, the lower part M₂ of the press descends, or moves awayfrom upper part M₁, following an S-shaped track (FIG. 4) carrying withit formed and cut object O, which therefore moves below the wastestarting material A. Subsequently moving base component M_(2f) of lowermould M₂ ceases its downwards movement while the remaining part of mouldM₂ continues to move downward, thus drawing out and releasing object Ocompletely from cavity M_(2c) of mould M₂.

At this point in the cycle there arises the difficult problem of movingor removing the thermoformed object or objects O from the forming areaand stacking them. Various systems have been proposed, and the two mostwidely in use will be described below.

The first is the air blowing system (FIG. 5) which consists of supplyingcompressed air along a main CL provided with nozzles U which producejets G which lift up objects O, causing them to tip slightly or toppleinto one or more collection channels R. The objects, continuing alongcollection channel R, become stacked forming a stack P.

This system can however only be used if the objects in mould M₂ arearranged in a single file.

If the objects in mould M₂ are in several rows (multiple files) the airjets G may remove objects O from the area bounded by parts M₁ and M₂ ofthe press, but they will be discharged in bulk. In order to get theseback into order and then stack them, it is necessary to have a suitablestacking device PL (FIG. 6), which is separate from the thermoformingmachine, but whose function must be synchronised therewith. Thisnaturally involves heavy additional costs, greater complexity inoperation and a high percentage of damaged objects which then have to berejected.

In thermoforming machines provided with a stacker PL, objects O are"removed" by blowing them out of the forming area and causing them toimpact against a stop surface AR before falling into a collecting bin V.At the base of collecting bin V there may be provided, as one of anumber of possible systems, a conveyor belt collector TR controlled by aMaltese cross device which has a plurality of panels hinged together,each of which has a hole W₁ which houses one object O. After impactingagainst surface AR which is orientated with a well-defined inclination,the objects end up by falling into holes W₁ to be then transportedintermittently towards a pusher I_(p) controlled by a toggle E whichpushes them one by one into a collection channel R where they form astack P.

This system, which is mentioned here by way of example as one of manysimilar types, has many disadvantages.

To begin with, only circular objects which are taller than particularminimum dimensions can be stacked. It is not therefore possible to stackobjects which are constrained to a specific orientation, e.g. objects ofrectangular shape.

Also, in falling and being mixed together in bin V, many objects becomedeformed or otherwise damaged.

For these reasons the known system illustrated in FIG. 6, and otherslike it, are now considered to be obsolete.

The second system using a suction plate is illustrated diagrammaticallyin FIG. 7 to 11 and is the object of Italian Patent No. 1,175,178.During the opening T of the press, which is effected by lower femalemould M₂, a suction plate PA is inserted between the upper edge B ofthermoformed object O, but blow waste A of the starting material, insuch a position that object or objects O can be sucked up when mould M₂has finished its descent T (press completely open).

Mould M₂ then stops in its lowest position to allow suction plate PA tomove away from the area bounded by dies M₁ and M₂ (forming area--FIG.8), carrying with its objects O to an area adjacent to the thermoformingmachine where they are picked up by suckers VS hinged on arms BG of astacker R (FIGS. 9 and 10). As soon as plate PA reaches the positionillustrated in FIG. 8, and is therefore outside the forming area, mouldM₂ begins its upwards movement, sheet material A advances by a furtherstep and a new thermoforming cycle is thus initiated. At the same timesuckers VS (FIG. 9) takes objects O from plate PA. By means of arotation of arm BG and a simultaneous rotation about pin Q suckers VSare turned over and carried against a multiple collector R where theobjects are stacked into stacks P (FIG. 10).

The difficulties and disadvantages which limit the performance of theextraction system in thermoforming machines with a single female mouldare:

1. The very long distance T by which the press must open, which is thesum of the height of the object or objects O and the distance travelledS (FIGS. 4 and 7) plus a specific distance to ensure a reasonable marginof safety (FIG. 7). However, as the time used in moving distance T istime which is of no use to the cycle it will be understood that, otherthings being equal, the output of the machine will be lower the tallerthe objects O which have to be removed.

2. Travel S is provided to create the space necessary for plate PA toinsert itself between material A and thermoformed object or objects O.Keeping travel distance S short implies creating problems with the sizeof suction plate PA. Increasing distance S means appreciably loweringthe productivity of the thermoforming machine. The definition of track Sand the dimensioning of plate PA are therefore always the result of acompromise. However the dimensions of suction plate PA are also governedby the requirement that it must not impede the advance of sheet materialA, which being in a heated state, has a tendency to weaken and falldownwards.

3. Keeping the press open for the time required for suction plate PA toenter and leave the forming zone increases the dead time in thethermoforming cycle (FIGS. 7, 8 and 13).

The fact that presses have to stand open for the time required forinserting plate PA between material A and object or objects O which haveto be removed, sucking up the objects and removing them (a time which iscommonly equal to 30% of the cycle time, i.e. a by no means negligibleperiod) has a greatly adverse effect on the productivity of the machine.

If relatively large objects or small objects in a number of rows arepresent in mould M₂ then the time for moving plate PA increases, becausethe distance T which has to be travelled is greater, or because plate PAhas to travel a back and forth distance which is at least equal to thewidth LA of mould M₂ (FIG. 7).

4. The time for which object or objects O remain n the press, that iswith their own walls in contact with the cooled wall of cavity of M_(2c)of mould M₂, is another important parameter which affects theproductivity of a thermoforming machine. In fact as soon as mould M₂reaches the position illustrated in FIG. 4, object O is displaced awayfrom the wall of cavity M_(2c) and therefore the stabilising cooling ofthe plastics material which has been subjected to thermoforming ceases.As may be seen from the diagram in FIG. 13, the cooling time tst forstabilisation in the press is the time between the injection of theforming air t₁ (through hole FO) and the start of removal t₃ (FIG. 4).Normally this time is equivalent to about half the cycle time. When itis necessary to increase cooling time tst the rate of the thermoformingmachine has to be slowed.

5. Because the objects are directly sent to the stacker from plate PA itis not possible to carry out any additional operations (e.g.perforation, labelling or the like) on objects O between the removaloperation and stacking.

If it is necessary to carry out additional operations on thermoformedand stacked objects O, the objects have to be repositioned, and thisusually means destacking them and sending them to suitable machines tocarry out the required operations, with a consequent risk of damagingthe objects and producing rejects.

One of the greatest disadvantages of thermoforming machines with suctionplate extraction lies in the shape and restricted dimensions of thesuction plate itself. In fact, with reference to FIG. 11, it will benoted how the pressure difference, between the external environment andthe negative pressure created by the suction through plate PA in thespace within thermoformed objects O, creates the force by which objectsO are attracted to and held against the plate. It can be said to a goodapproximation that this pressure difference is equal to the loss of headwhich air flows Q1/2 and Q2/2 and Q3/2 create when passing through slotsFE along edges BO.

Within Plate PA then:

the air in section S₁ will have a velocity V₁ which will cause a flow Q1to pass,

in section S₂ it will have a speed V₂ which is different from V₁ andsuch as to pass a flow Q1=Q2.

in section S₃ the speed will be V₃ which is different from V₁ and V₂ andsuch as to cause the passage of a flow equal to Q1+Q2+Q3. Idealoperating conditions arise when Q1=Q2=Q3. As suction plate PA has to beinserted between sheet material A and the upper edges BO of objects O,its height dimension must be as small as possible so as not to constrainthe distance by which the press opens and make it excessively long. Inpractice therefore it is preferable to use a configuration in which V₃is very much greater than V₁, so that when it is in operation Q1 isgreater than Q2, which is in turn greater than Q3. This means that thesystem operates under conditions which are very far from optimumconditions.

In thermoforming machines which have double lower female mould of thetype disclosed in Italian Patent No. 1,053,243 and illustrateddiagrammatically in FIG. 12, the objects are formed by alternatelycoupling the two female parts M_(2s) and M_(2d) with the single uppermale part M₁.

When dies M₁ and M₂ are closed the thermoforming takes place in themanner described above in stages 1 and 3.

With such machines it is possible to obtain advantages in subsequentstages, in that:

1) The distance T travelled by the press on opening its independent ofthe depth or height of the thermoformed objects and may therefore bekept at a minimum value sufficient to feed in material A, with a greatreduction in the passive time in the cycle, as is shown in the diagramin FIG. 13.

2) The press remains open only for the time necessary to advance sheetmaterial A and effect the alternate lateral movement of female mouldsM_(2s) and M_(2d). These operations take place at the same time, withoutproviding any stoppage for removing thermoformed objects O.

3) The time for which objects O remain in cavity M_(2c) with their wallsin contact with the mould is longer than the thermoforming cycle (FIG.13), because objects O remain in close contact with the die from thetime of cutting until the next thermoforming operation in the otherfemale mould. In other words the cooling of a thermoformed object O isextended throughout the following stages:

forming, for example in M₁ -M_(2s)

cutting out

press opening

lateral movement of the double female mould

closing of dies M₁ -M_(2d)

forming in M₁ -M.sbsb.2_(d)

The stacking of objects O on these thermoforming machines takes place instacker R_(s) in the case of the objects formed in M_(2s) during formingstage in mould M_(2s) and R_(d) in the case of those formed in M_(2d).

Base members M_(2fs) and M_(2fd) remove objects O by travelling distanceC_(t) (FIG. 12) and stack them alternately pushing the objects formed infemale mould M_(2s) into left hand collection or stacking device R_(s)and those formed in female mould M_(2d) into right hand collection orstacking device R_(d). Devices R_(s) and R_(d) are located to the sidesof the fixed part of die M₁. It may happen therefore that objects Owhich have recessed angular supporting portions (e.g. 2, 3, 4 or moreindentations or indented feet located at the same level) provided, as isusual in the art, to prevent one object binding completely withinanother during stacking, (which would make it impossible for the objectsto be then destacked for use), are located in a perfect verticalorientation and alignment, because they all come from the same mould. Inthis case it will be seen that there is accurate superimposition of twoor more consecutive stacked objects, so that the spacing effect of thefeet or indentations is neutralised and as a result the objects bindfirmly together making it difficult to separate them.

Another cause of poor spacing and therefore of irreversible bindingbetween the stacked thermoformed objects lies in inaccurate forming ofthe stacking feet or indentations (which generally project towards theinterior of the object by a fraction of a millimetre or a little more),as, being made of a thermoplastics material which is thereforedimensionally unstable at the time of forming, these are obtained withfairly wide dimensional tolerances. There will therefore be variationsin the connecting angle to both the feet and the base of each object,depending on the nature of the thermoplastics material used, and theshape and depth of the objects being thermoformed, which areunacceptable for correct stacking of the objects.

Objects which do not destack, or which destack with difficulty, requiremanual intervention, reduce productivity and almost always end up byincreasing the number of rejects.

As will be noted, the distance C_(t) travelled by base members M_(2fs)and M_(2fd) depends on the maximum height of the objects O being formedand is therefore longer when the objects are deeper. It is essential infact that interference between the bottom of object O and the lateralmovement and closing of the press is avoided.

FIG. 12 illustrates pins S_(p) which centre parts M_(2s) and M_(2d) withrespect to fixed part M₁ as the press closes, through being inserted bya certain amount into corresponding seats Z provided in mould M₂. A₁also indicates diagrammatically the members which feed or advance sheetmaterial A.

As in thermoforming machines having a single female mould, so inmachines having a double female mould, stacking of the objects takesplace without there being any practical possibility of carrying outadditional operations on thermoformed objects O, as these are gatheredinto stacks immediately after thermoforming.

SUMMARY OF THE INVENTION

An object of this invention is to eliminate or substantially to reducethe disadvantages described above which arise with known thermoformingmethods and machines and forms of extraction.

Another object of this invention is to provide a method for theextraction of thermoformed objects from the forming zone by making useof a suction plate which is not subject to critical dimensionalconstraints.

A specific object of this invention is to make it possible to carry outa whole series of additional and/or auxiliary operations on thethermoformed objects during each thermoforming cycle, while keeping theobjects outside the press in the same mutual positions which theyoccupied in the forming mould.

Another object of this invention is to provide a substantial reductionin the open press waiting time in order to improve productivity andefficiency.

Another object of this invention is to effect a drastic reduction of upto one half in the height of the press, with a consequent reduction inthe masses in movement, the cost of manufacturing the press itself and asubstantial increase in the speed of movement or lateral movement of thepress.

Yet another object of this invention is to provide the production ofthermoformed objects which may be finished through one or moresupplementary operations carried out at the same time as a thermoformingoperation before stacking and packaging, without it being necessary torestart processing.

In accordance with a first aspect of this invention, a method isprovided for the thermoforming of hollow objects having a base from asheet of thermoplastics material, which effects in one singlepredetermined working cycle:

the production of a pressed object by hot forming and cutting out of theobject or objects between one half of a movable double female mouldwhich is located in the forming area opposite a male die,

Movement of the female half of the mould, said half carrying thethermoformed object or objects therewithin, towards a correspondingdischarge area alternately to one side or the other of the forming area,

removing the object or objects from the female half of the mould in itscorresponding discharge area and transferring each object to one of aplurality of receiving formers of a shape corresponding to the mould,which formers can move sequentially in steps along a track,

sequential movement of the formers towards least one workstation orhandling station at the same time as the female mould moves back tobring its other half opposite the male die in order to produce asubsequent formed object, and

carrying out at least one processing or handling operation on all theobjects carried by at least one former at the same time as the nextformed object is produced.

In accordance with a further aspect of this invention there is providedapparatus for the thermoforming of hollow objects incorporating a basefrom a sheet of thermoplastics materials, comprising

a male die and a double female mould, one half of which mould can movealternately with respect to the other half for mating with the male diein turn while at the same time carrying the object or objects producedpreviously in the other half of the female mould to an easily accessibledischarge area,

a sheet feed to deliver a sheet of thermoforming material in stepsbetween the male and female moulds,

a cutting device which is brought into operation at the end of eachclosing movement of the press,

a stepwise conveyor having a plurality of plates or formers, each ofwhich is capable of receiving and supporting the object or objects fromone forming operation in the same mutual positions which they occupiedin the press,

at least one pick-up head capable of lifting one set of formed objectsalternately from each half of the double female mould from one side orthe other of the male die and of transferring them to a correspondingplate or former on the conveyor and

at least one processing or handling station located along the conveyorfor the simultaneous handling or processing of all the objects from atleast one forming operation.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be further illustrated, by way of example,with reference to FIGS. 14 to 33 of the accompanying drawings, in which:

FIG. 14 is a front elevational view in schematic form of part of aconveyor utilised in the apparatus of the invention,

FIG. 15 is a plan view of the device of FIG. 14,

FIGS. 16 and 17 are respectively a plan view and a magnified plan viewsimilar to that shown in FIG. 15, but with the pick-up heads in adifferent stage of the working cycle,

FIGS. 16A and 16B are respectively partial views from above on amagnified scale of the two halves of a double female mould,

FIGS. 18 and 19 are elevational views in schematic form of thethermoforming press in two different stages of operation without thestepwise conveyor,

FIG. 20 is a view from below and on a magnified scale of a portion ofthe pick-up head,

FIGS. 21A, 21B and 21C show details of FIG. 19 on a magnified scale,

FIG. 22 illustrates a detail of FIG. 14 on a magnified scale,

FIG. 23 is a view similar to that of FIG. 14, but in a different stagein the operating cycle,

FIG. 24 shows a detail of FIG. 23,

FIG. 25 is a front elevational view of a stacker which can be useddownstream of the stepwise conveyor, during the loading stage,

FIG. 25A shows a detail of FIG. 25 on a magnified scale showing themanner in which the thermoformed objects are stacked,

FIG. 26 shows a detail of FIG. 25 on a magnified scale,

FIG. 27 shows the stacker of FIG. 25 during the stage of dischargingonto a plate,

FIG. 28 shows a detail of FIG. 26 in a position ready for discharging,

FIG. 29 shows the stacker of FIG. 25 in a position for horizontaldischarging,

FIGS. 30 and 31 diagrammatically illustrate successive stages in thehorizontal discharging of the stacker of FIG. 29,

FIG. 32 shows a variation with respect of FIG. 23, and

FIG. 33 shows a diagram of the thermoforming stages and cycle times forthe equipment illustrated in FIGS. 14 to 31, for comparison with thediagram of FIG. 13.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the figures listed above, it will be noted that thethermoforming means or press according to this invention comprises asupporting structure 1 on which is mounted a fixed upper plate 2 bearinga male die 3, which in the example illustrated is also fixed, a slidingdie-supporting table 4, which is e.g. supported on roller feet suitablefor high loads with automatic lubrication (not shown in the drawing) tomake horizontal movements (arrow A), and a lower plate 5 which can movein a vertical direction (arrow B--FIG. 18) which is driven by e.g. twotoggle units (not shown). Sliding table 4 supports two female moulds (adouble female mould) 6 and 7 which are identical and are locatedalongside each other at the same level, which are intended to be movedby the sliding table 4 alternately beneath the fixed die 3 where theyare caused to rise up and mate against the die and successively open bybeing lowered in order to be moved laterally with respect to the fixeddie 3. In other words, mould 6 is moved to the left and mould 7 is movedto the right (as seen in the Figs. in the drawing) with respect to thefixed die 3.

A sheet 8 of thermoplastics material, which may be wound on to a mandrelor be derived directly from an extrusion unit combined with thethermoforming device, is made to advance by means of a chain feedindicated generally by reference numeral 9, in a direction normal tothat of the movement of double female mould 6, 7 beneath fixed die 3 butabove double female mould 6, 7, in steps, in time with the rate ofpressing or forming.

As will be better seen in FIGS. 18 and 19, fixed die 3 may have aplurality of depressions 10 each of which has an open lower end boundedby a free edge 11 (FIGS. 21A and 21B) and houses a corresponding maleplug 12 fixed at the end of a corresponding vertical control rod 13slidably mounted between the upper wall of the fixed die and extendingbeyond it to meet and be joined to an upper activating bar or plate 14,which is in turn controlled by activating means, not shown in thedrawings, e.g. of a type well-known to those skilled in the art. The twofemale moulds 6 and 7 each have a plurality of upwardly open cavities 15equal in number to the number of depressions 10 and having the samespacing, in such a way that when a female mould mates with the fixed dieeach depression or pit 10 accurately mates with a corresponding cavity15 below.

Centering means comprising e.g. four pins 16 borne by upper plate 2,which are fixed or which can be caused to project to engage incorresponding receiving seats 17 provided in the female mould when thedies are closed together are provided for correct mating between femalemoulds 6 and 7 and fixed die 3.

The base of each cavity 15 is equipped with an extraction device (FIGS.18, 19, 21A, 21B and 21C) comprising a head 18 which can move upwards asit is controlled by a corresponding rod 19 which is integral with acontrol bar or plate 20, which is intended to release and push out oneor more thermoformed objects 150 from between the press after the dieshave opened.

Advantageously, each cavity 15 may have a constriction 21 forming a steparound the formed object, the height of which from the base of thecavity defines the stacking height H for formed objects 150 (FIG. 21A).

Lower plate 5 is driven by suitable units (not shown), for example twotoggle units, in order to effect the vertical closing and openingmovements between female moulds 6, 7 and fixed die 3.

Two eccentrics, which by causing plate 5 to move through a smalldistance make it possible to cut out and separate the objects from thesheet, may be provided beneath the base of the two toggle units. Thisoperation, as is usual in the art, is carried out during the closure offemale moulds 6, 7 against fixed die 3.

Fixed upper plate 2 has two vertical supporting columns 22 and 23 (FIGS.15, 16 and 17), on each of which is rotatably mounted a correspondingprojecting arm 24, 25 which at its free end bears a suction pick-up head26, 27, which is constructed e.g. in the shape of a bell cup which isclosed off at the base by a perforated suction plate 28 communicatingwith a source of vacuum or negative pressure above in order to draw outthe air, such as a suction pump, which is not shown, by means of aflexible conduit 26a and 27a. As may be better seen in FIG. 20, plate 28has a plurality of through holes 29 placed in an orderly arrangement ata distance from the intersection of longitudinal 30 and transverse 31suction grooves, advantageously with a spacing equal to that of cavities15 in female moulds 6 and 7.

Arms 24 and 25 are located on one side respectively of fixed die 3 andare caused to move angularly about columns 22 and 23 between a positionin which corresponding pick-up head 26 and 27 is above a correspondingfemale mould 6 or 7, when this is moved laterally completely away fromfixed die 3, and a position outside the thermoforming machine by acorresponding motor/reduction gear unit 32, 33 driven in such a way asto cause pick-up heads 26, 27 to make rhythmical angular movements intime with the back and forth alternating movements of moulds 6 and 7 inorder to effect the transfer of thermoformed objects 150, as will befurther described hereinafter.

Within the radius of action of arms 24 and 25 there is located astepwise conveyor 35 (FIGS. 14, 15, 16, 22 and 23) , which is formed oftwo sliding and supporting sides or banks 36, a plurality of plates orformers 37 slidably supported by the sides and drawn at their twoopposite ends by a pair of chains 38 which pass round a pair ofchainwheels 39 at the ends of the conveyor (FIG. 22). Each plate orformer 37 has an intermediate pin 40 providing an articulation to achain 38 and two lateral rollers or pin 41 and 42 at each end thereofwhich engage with the chains. Alongside the banks 36 rollers 41 and 42are free or may run along corresponding straight upper 43 and lower 44guides or rails, while at the transmission end of the conveyor, pin 40is caused to follow a circular path around a wheel 39, the front roller(with respect to the direction of movement, e.g. roller 41 in FIG. 22)is caused to follow a track which is also circular along a correspondingfixed guide 45 which has the same radius of curvature as the originalcurvature of the wheel 39 and the rear roller (roller 42 in FIG. 22) isengaged between two radiused teeth 46 of a wheel 47 which has its ownaxis of rotation along the line of the wheel 39 and the said pitch line.With this arrangement, at the ends of conveyor 35 each plate or former37 is returned to a position which is always parallel to the otherplates or formers and when in the discharge position is relatively farfrom the plate or former which preceded it and the one which follows it.

It is therefore possible to provide a treatment or processing station 50(FIGS. 14 and 23) and a stacking station 51 at the transmission ends ofconveyors 35 and possible intermediate treatment or processing stationsas will be described below.

Processing station 50 is designed to perform various operations onformed objects 150, which are located in an easily accessible positionfor working units provided at the said station, while in stackingstation 51 the formed objects can be stacked before finally beingremoved from conveyer 35.

Plates or formers 37 each have a plurality of holes or seats 37a havingthe same diameter (or a slightly smaller diameter) and the same spacingsas cavities 15 in female moulds 6 and 7, so that they can receive theobjects obtained from a forming operation transferred thereto by heads26 and 27. Plates or formers 37 are moved stepwise along an upper trackalong conveyor 35, along which they receive formed objects 150 fromheads 26 and 27 alternatively, are stopped sequentially in a stepwisemanner at processing station 50 and are then passed along a lower trackto reach stacking station 51.

Treatment or processing station 50 may be designed to carry out anydesired additional operation, such as e.g. perforating the bases ofshaped objects 150, dry printing or stamping of the objects, labelling,filling with soluble beverage powders, sterilisation, etc.

In FIGS. 14 and 23, station 50 is illustrated by way of example by atoggle driven drilling head equipped with drilling bits 52 arranged withthe same spacing as holes 37a and formers 37 and operated with the sameoperating rhythm as stepwise conveyor 35.

However any other suitable operating unit capable of carrying out adesired process or manipulation upon the formed objects may be providedinstead of or in association with toggle-operated driving unit 50.

Stacking station 51 (FIGS. 14 and 23 to 29) comprises a supporting frame53 upon which is located the downstream end of conveyor 35, a lowerpusher 54 which can be driven in an alternating vertical back and forthmotion in time with the stepwise operation of conveyor 35 and having aplurality of pusher heads 55 equal in number to and having the samespacing as holes 37a in formers 37, and a stacker 56 placed aboveconveyor 35 in vertical alignment with pusher 54. Stacker 56 may be ofany suitable type, e.g. having a plurality of parallel tubular rods 57held together by a frame 58 (FIG. 25) on which is also slidably mountedan upper pusher 59 which can also be driven in an alternating back andforth motion as will be described below.

Each rod 57 is advantageously provided with teeth 60 (FIGS. 26 and 28)which are retractable in that they are hinged about a transverse axis 61so that they can be moved angularly between a position in which they arewithdrawn into the rod (FIG. 28) so that objects 150 can slide betweenthe rods and a position in which they project from the rod (FIG. 26) toengage an edge 151 of an object 150.

As will be better seen from FIGS. 16A, 16B and 25A, it is possible toarrange matters in such a way that female mould 6 produces objectsidentical to those produced in female mould 7, but having e.g. four feetor indentations 152 offset by a predetermined angle in such a way thatgiven that the stacks of objects at station 51 are formed from objectsderiving from mould 6 and mould 7 alternately, because these are loadedonto formers 37 of conveyor 35, the flat part of the base of an object150 (even when the bottom edge has a relatively large connecting angle)is always brought to rest against a sufficient number of feet 152.

A similar result is achieved if instead of having a different angularorientation of feet 152 in the two female moulds, a different number offeet 152 are provided. This naturally makes it possible to have aperfect stacking arrangement at all times without any risk of permanentor irreversible binding between objects 150 and thus reducing the numberof rejects.

Stacker 56 is supported on a trolley structure 62 which can run by meansof wheels 63 along a beam or section 64 to transfer a plurality ofstacks of objects 150 from stacker 56, e.g. onto a standing andsupporting surface 65, which may if desired be capable of being raisedand lowered, as shown diagrammatically in FIGS. 25 and 27.

Beam 64 may be rotatably supported around its own longitudinal axis 66and may have angular projections around it through a toothed section 67which engages a toothed pinion 68 keyed onto drive shaft 69 of amotor/reduction gear unit 70. With this arrangement, stacker 56 can beinclined through 90 degrees or any intermediate angle thus placing it,for example, in a horizontal position and setting it down onto asupporting platform 71 (FIGS. 29 to 31). Platform 71 is designed toperform a stepwise descending movement (through a transmission 72, ascrew 73 and a corresponding nut) to enable a transverse expeller 74 totransfer a row of stacked objects 150 to a cage conveyor 75 whichcarries the stacked objects to e.g. a packing station.

The functioning of the means described above is extremely simple. Whenthe press is open a predetermined length of sheet 8 is caused to advanceby means of chain feed 9 beneath fixed die 3, whereupon female mould 6or 7 (e.g. die 6) which is located beneath the fixed die is raised andmated against die 3 with the consequent thermoforming of objects 150 andthe subsequent cutting thereof. Mould 6 together with mould 7 movedownwards to open the press and immediately afterwards mould-bearingtable 4 moves laterally so as to carry mould 6 completely away fromfixed die 3 and mould 7 beneath die 3 ready for the next thermoformingcycle.

In the meantime pick-up head 26 is moved into the extraction area abovefemale mould 6, which is now completely unobstructed, and as soon asmould 7 closes against the fixed die it removes formed objects 150 frommould 6, which had been previously removed or loosened from cells 15 byheads 18 of the extraction device. Rotating around its column 22 (FIG.16) head 26 moves above a former 37 on conveyor belt 35 and depositsformed objects 150 into an identical number of holes 37a (FIGS. 15 and16).

In the subsequent forming, cycle pick-up head 27 moves over mould 7which has been moved laterally with respect to fixed die 3 into theextraction area and, with a similar movement to that of head 26,transfers formed objects from mould 7 to former 37 on conveyor 35 in asimilar way. In this way, head 27 will set objects 150 down on alternateformers on the conveyor. The same will be done by pick-up head 26, buton the formers left unoccupied by head 27, so that all formers 37 arefinally filled with objects 150 before they are delivered to processingstation 50.

It will be noted that the fact that each formed object is transferred tostepwise conveyor 35 and remains there makes it possible to extend thestabilisation times tst outside the press considerably, which is anadvantageous feature for improving the quality of formed objects 150. Infact in the example illustrated objects 150 are supported on the formersof conveyor 35 for seven or more thermoforming cycles.

From time to time it is possible to sample objects 150 from a former 37selected at random to check the quality of objects 150 without thisproducing the slightest disturbance in the equipment's operating cycle.

At workstation 50 the objects are processed or partly filled with powdermaterial, or labelled etc., and are then passed along the lower portionof conveyor 35 towards stacking station 51, from which they are removedin stacks to be delivered for use or to a packing station for delivery.Even while they are moving along the lower portion of the conveyor theyundergo prolonged stabilisation, and remain in the same mutual positionsas they had in the thermoforming press.

It will be noted how, in addition to providing easy and uniform controlof the internal negative pressure over the whole working surface ofplate 28, the use of suction pick-up heads 26 and 27 is applicable toall applications and is not dependent on the existence of an edge 151 onthe objects being picked up. Also, contrary to the situation inconventional systems, through the use of heads 26 and 27 the movementfor extracting objects 150 from the presses is equal to the stackingheight H (FIG. 21A).

More particularly, with reference to FIG. 21B when a mould 6 or 7 (e.g.mould 6) is moved into the extraction or discharge position, head 26 ismoved into a position above mould 6 at the same time, as alreadymentioned. The distance ho which extraction device 18 and 20 has to movefor partial extraction of objects 150 before these are picked up by head26 is effected while part 7 of the press is carrying out anotherthermoforming cycle. This also applies to the subsequent extractionmovements performed by head 27, for its rotation and the deposition ofobjects 150 and formers 37 and to its return into position above mould 7so that no dead times are added to any of the forming cycles.

This means that waiting times during which the press is open, which asmentioned above with reference to thermoforming machines with a suctionplate which enters into the pressing or forming area itself represents30% of the thermoforming cycle, are drastically reduced.

It will also be noted how the removal of objects 150 is only partlyentrusted to the movement of the heads or bases 18. The objects are infact removed (FIG. 21C) by means of the movement separating the mouldand the plate, partly caused by lowering of the mould and partly by theraising of bases 18. Because these movements take place simultaneouslywith other dead times in each forming cycle they do not affect theproductivity of the equipment.

If a comparison is made between the machine according to the known stateof the art in FIG. 11, it will easily be noted that, if

ho is the height of objects 150,

hp is the height of control plate 20,

ha is the length of the approach travel for stacking, and

hs is the dimension (height) of a double female mould 6, 7, the totalheight H of a mould M_(2s) and M_(2d) in FIG. 12 will be the sumHo=hp+ho+ha+hs.

The height of female moulds 6 and 7 in FIG. 21B according to thisinvention is instead H=hp+ha+hs, that is H is Ho less than an amountequal to at least the maximum height of the thermoformed objects 150.Because the height Ho of the mould in a conventional machine withstacking is usually slightly greater than twice the height of thethermoformed objects, it can be concluded that the extraction performedby heads 26 and 27 in the appropriate extraction or discharge areascompletely outside the pressing area and away from fixed die 3 at leasthalves the height of female moulds 6 and 7.

The reduction in the height of the moulds brings about an appreciabledecrease in their weight, and therefore their inertia, which means thatmore rapid lateral movements can be performed.

Also, it will be noted from FIG. 21B that mould 7 is illustrated in theextraction or discharge position. The fact that mould 7 is moved in aposition completely outside the pressing or thermoforming area has madeit possible to dimension suction heads 26 and 27 in such a way that thesum of the flows (Q1+Q2+Q3) all passes through section Hpe. In sectionsS1, S2 and S3 the rates of flow will be identical in each and thereforethe value of the pressure pi which is set up within the head will beuniform over the entire surface of plate 28. This has the result ofoptimising the most important parameter for the satisfactory operationof a pick-up head 26, 27, with the result that it is possible to achievethe optimum condition in which Q1=Q2=Q3.

The invention described above may be subjected to numerous modificationsand variations within the scope thereof. Thus, for example, conveyor 35may be replaced by a conveyor with an empty return track, or with emptyformers 37, after being passed around a terminal return wheel ofconsiderable diameter or a number of return wheels in such a way thatstations 50 and 51 can operate on its upper track. Here again processingstations 50 may be more than one in number and may be arranged insequence along the conveyor.

If desired, station 50 may be omitted or in any event may be leftinactive for particular types of object 150.

Furthermore,as illustrated in FIGS. 23 and 32, a suction hood 80 for thevolatile residues produced from thermoplastic material A which is usedfor the thermoforming of objects 150 may advantageously be provided inany suitable position above, around or below conveyor 35. A tunneltreatment chamber 85, e.g. for sterilization and/or heat conditioning,which may surround at least one portion of conveyor 35 and which may beprovided with a plurality of needles 86 intended for the injection of afluid, such as cold air, to achieve optimum stabilization o objects 150outside the press is also illustrated diagrammatically in FIG. 32.

If desired, downstream of each pick-up head 26 and 27 a rim curlingworkstation is arranged to form curled rims on all the objects formed inthe same moulding operation immediately after they have been dischargedon a plate or former 37. In this case the conveyor 35 has acorrespondingly greater length by at the least two plates or formers,whereby making it possible for the objects to be formed with a curledrim within the cyclic time while being still hot as they have just beenpicked up from the mould 6 or 7, and thus there is no need to heat themjust for the rim finishing operation before reaching the processingstation 50.

Materials and dimensions may be varied in accordance with requirements.

I claim:
 1. A method for thermoforming an object from a sheet ofthermoplastics material, the method comprising:producing the object byhot forming and cutting out the object between one half of a movabledouble female mold and an opposing male die, the one half of the femalemold and male die being located in a forming area; moving the one halfof the female mold from the forming area to a discharge area, the onehalf of the female mold containing the object therewithin, andsimultaneously moving the other half of the female mold from thedischarge area into the forming area opposite the male die to produce afurther object; picking up the object from the half of the female moldwhile in the discharge area and transferring the object to one of aplurality of receiving formers each having a shape corresponding to thefemale mold, the receiving formers being sequentially moved in astepwise fashion along a track; sequentially moving the formers at thesame time as the one half of the female mold moves into the dischargearea and the other half of the female mold moves from the discharge areainto the forming area opposite the male die; and performing at least oneprocessing operation on the object carried by at least one former at thesame time as the further object is produced.
 2. The method as claimed inclaim 1, further comprising moving away the object processed in thereceiving former at the same time as the further object is transferredto a receiving former.
 3. The method as claimed in claim 1 wherein aplurality of objects are formed.
 4. The method as claimed in claim 3,wherein the processing operation comprises stacking the objects.
 5. Themethod as claimed in claim 3, wherein the stacking of the objects from aformer occurs simultaneously with at least one other processingoperation on the object in another former.
 6. The method as claimed inclaim 1, wherein the processing operation comprises perforating a baseof the object.
 7. The method as claimed in claim 1, wherein theprocessing operation comprises labeling of the object.
 8. The method asclaimed in claim 1, wherein the processing operation comprisessterilization of the object.
 9. The method as claimed in claim 1,wherein the processing operation comprises prefilling the object with apredetermined quantity of a product packed in the object.
 10. The methodas claimed in claim 1, wherein the processing operation comprisesforming a curled rim on the object using heat from the hot forming. 11.The method as claimed in claim 1, further comprising stabilizing theobject on the receiving formers for a time equal to at least sevenconsecutive thermoforming cycles.
 12. The method as claimed in claim 3,wherein the processing operation comprises extracting at least oneobject for quality control while the object is on the receiving former.